Frame formats for channel bonding and mimo transmissions

ABSTRACT

Certain aspects of the present disclosure provide methods and apparatus for preamble structures for transmissions sent using channel bonding (across multiple channels) and/or MIMO (with two or more spatial streams).

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present application for patent claims benefit of U.S. ProvisionalPatent Application Ser. No. 62/089,815 (Attorney Docket number150982USL), filed Dec. 9, 2014, assigned to the assignee hereof andhereby expressly incorporated by reference herein.

FIELD

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to frame formats fortransmissions using techniques such as channel bonding andmultiple-input multiple-output (MIMO).

BACKGROUND

In order to address the issue of increasing bandwidth requirementsdemanded for wireless communications systems, different schemes arebeing developed to allow multiple user terminals to communicate with asingle access point by sharing the channel resources while achievinghigh data throughputs. Multiple-input multiple-output (MIMO) technologyrepresents one such approach that has recently emerged as a populartechnique for next generation communication systems. MIMO technology hasbeen adopted in several emerging wireless communications standards, suchas the Institute of Electrical and Electronics Engineers (IEEE) 802.11standard. The IEEE 802.11 standard denotes a set of Wireless Local AreaNetwork (WLAN) air interface standards developed by the IEEE 802.11committee for short-range communications (e.g., tens of meters to a fewhundred meters).

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, where N_(S)≦min {N_(T), N_(R)}. Each of the N_(S) independentchannels corresponds to a dimension. The MIMO system can provideimproved performance (e.g., higher throughput and/or greaterreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

In wireless networks with a single Access Point (AP) and multiple userstations (STAs), concurrent transmissions may occur on multiple channelstoward different stations, both in the uplink and downlink direction.Many challenges are present in such systems.

SUMMARY

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes a processingsystem configured to generate a frame for transmission on a plurality ofchannels, the frame having first information comprising at least one ofpreamble, channel estimation, or header information decodable and forprocessing by first and second types of devices, and wherein the firstinformation is repeated in each of the plurality of channels duringtransmission of the frame, second information comprising at least one ofpreamble, channel estimation, or header information decodable and forprocessing by the second type of device, and wherein the secondinformation occupies gaps between the channels during transmission ofthe frame, and a portion spanning the plurality of channels and thegaps; and an interface for outputting the frame for transmission.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes an interfacefor obtaining a frame having first information comprising at least oneof preamble, channel estimation, or header information decodable and forprocessing by first and second types of wireless devices, the firstinformation is repeated in each of the plurality of channels, secondinformation comprising at least one of preamble, channel estimation, orheader information decodable and for processing by the second type ofdevice, and wherein the second information occupies gaps between thechannels, and a portion spanning the plurality of channels and the gaps;and a processing system configured to process the first information andgenerate a channel estimate based, at least in part, on the secondinformation, and to decode at least some of the portion of the framebased on the channel estimate.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes a processingsystem configured to generate a frame for transmission on at least onechannel, the frame having: a preamble portion comprising firstinformation comprising at least one training field detectable by otherapparatuses, the first information to be transmitted on a set of one ormore sub-channels, each sub-channel comprising a fractional portion ofthe full bandwidth of the at least one channel, and second informationcomprising at least one of channel estimation or header information, thesecond information to be transmitted using the full bandwidth of the atleast one channel, and a data portion to be transmitted using the fullbandwidth of the at least one channel; and an interface for outputtingthe frame for transmission.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes an interfacefor obtaining a frame having a preamble portion comprising firstinformation comprising at least one training field detectable by otherapparatuses, the first information to be transmitted on a set of one ormore sub-channels, each sub-channel comprising a fractional portion ofthe full bandwidth of the at least one channel, and second informationcomprising at least one of channel estimation or header information, thesecond information to be transmitted using the full bandwidth of the atleast one channel; and a data portion transmitted using the fullbandwidth of the at least one channel; and a processing systemconfigured to process the first information and generate a channelestimate based, at least in part, on the second information, and decodeat least some of the data portion of the frame based on the channelestimate.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes a processingsystem configured to generate a frame for transmission on at least onechannel, the frame having: first information comprising at least one ofa training field, channel estimation, or header information forprocessing by first and second types of devices, and extended headerinformation intended for processing by only a second type of device thatis a targeted recipient of the frame; and a data portion to betransmitted on the at least one channel; and an interface for outputtingthe frame for transmission.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes an interfacefor obtaining a frame transmitted on at least one channel, the framehaving: first information comprising at least one of a training field,channel estimation, or header information for processing by first andsecond types of devices, and extended header information intended forprocessing by only a second type of device that is a targeted recipientof the frame; and a data portion to be transmitted on the at least onechannel; and a processing system configured to process the firstinformation and decode at least some of the data portion of the framebased on the extended header information.

Aspects of the present disclosure also provide various methods, means,and computer program products corresponding to the apparatuses andoperations described above.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a diagram of an example wireless communications network, inaccordance with certain aspects of the present disclosure.

FIG. 2 is a block diagram of an example access point and example userterminals, in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates an example mixed mode preamble format.

FIG. 4 is a flow diagram of example operations for generating a packetwith preamble information transmitted in channel gaps, in accordancewith certain aspects of the present disclosure.

FIG. 4A illustrates example means capable of performing the operationsshown in FIG. 4.

FIG. 5 is a flow diagram of example operations for processing a packetwith preamble information transmitted in channel gaps, in accordancewith certain aspects of the present disclosure.

FIG. 5A illustrates example means capable of performing the operationsshown in FIG. 5.

FIGS. 6 and 7 illustrate example frame formats, in accordance withcertain aspects of the present disclosure.

FIG. 8 is a flow diagram of example operations for generating a packet,in accordance with certain aspects of the present disclosure.

FIG. 8A illustrates example means capable of performing the operationsshown in FIG. 8.

FIG. 9 is a flow diagram of example operations for processing a packet,in accordance with certain aspects of the present disclosure.

FIG. 9A illustrates example means capable of performing the operationsshown in FIG. 9.

FIGS. 10-12 illustrate example frame formats, in accordance with certainaspects of the present disclosure.

FIG. 13 is a flow diagram of example operations for generating a packet,in accordance with certain aspects of the present disclosure.

FIG. 13A illustrates example means capable of performing the operationsshown in FIG. 13.

FIG. 14 is a flow diagram of example operations for processing a packet,in accordance with certain aspects of the present disclosure.

FIG. 14A illustrates example means capable of performing the operationsshown in FIG. 14.

FIGS. 15-18 illustrate example frame formats, in accordance with certainaspects of the present disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure provide techniques for reducinglatency in systems including legacy devices by transmittinglegacy-decodable preamble information in each of multiple channels andfor transmitting preamble information for channel estimation of amulti-channel transmission in gaps between the multiple channels.

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

An Example Wireless Communication System

The techniques described herein may be used for various broadbandwireless communication systems, including communication systems that arebased on an orthogonal multiplexing scheme. Examples of suchcommunication systems include Spatial Division Multiple Access (SDMA),Time Division Multiple Access (TDMA), Orthogonal Frequency DivisionMultiple Access (OFDMA) systems, Single-Carrier Frequency DivisionMultiple Access (SC-FDMA) systems, and so forth. An SDMA system mayutilize sufficiently different directions to simultaneously transmitdata belonging to multiple user terminals. A TDMA system may allowmultiple user terminals to share the same frequency channel by dividingthe transmission signal into different time slots, each time slot beingassigned to different user terminal. An OFDMA system utilizes orthogonalfrequency division multiplexing (OFDM), which is a modulation techniquethat partitions the overall system bandwidth into multiple orthogonalsub-carriers. These sub-carriers may also be called tones, bins, etc.With OFDM, each sub-carrier may be independently modulated with data. AnSC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit onsub-carriers that are distributed across the system bandwidth, localizedFDMA (LFDMA) to transmit on a block of adjacent sub-carriers, orenhanced FDMA (EFDMA) to transmit on multiple blocks of adjacentsub-carriers. In general, modulation symbols are sent in the frequencydomain with OFDM and in the time domain with SC-FDMA.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of wired or wireless apparatuses (e.g.,nodes). In some aspects, a wireless node implemented in accordance withthe teachings herein may comprise an access point or an access terminal.

An access point (“AP”) may comprise, be implemented as, or known as aNode B, a Radio Network Controller (“RNC”), an evolved Node B (eNB), aBase Station Controller (“BSC”), a Base Transceiver Station (“BTS”), aBase Station (“BS”), a Transceiver Function (“TF”), a Radio Router, aRadio Transceiver, a Basic Service Set (“BSS”), an Extended Service Set(“ESS”), a Radio Base Station (“RBS”), or some other terminology.

An access terminal (“AT”) may comprise, be implemented as, or known as asubscriber station, a subscriber unit, a mobile station, a remotestation, a remote terminal, a user terminal, a user agent, a userdevice, user equipment, a user station, or some other terminology. Insome implementations, an access terminal may comprise a cellulartelephone, a cordless telephone, a Session Initiation Protocol (“SIP”)phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, a Station (“STA”), or some other suitable processing deviceconnected to a wireless modem. Accordingly, one or more aspects taughtherein may be incorporated into a phone (e.g., a cellular phone or smartphone), a computer (e.g., a laptop), a portable communication device, aportable computing device (e.g., a personal data assistant), anentertainment device (e.g., a music or video device, or a satelliteradio), a global positioning system device, or any other suitable devicethat is configured to communicate via a wireless or wired medium. Insome aspects, the node is a wireless node. Such wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as the Internet or a cellular network) via a wired orwireless communication link.

FIG. 1 illustrates a multiple-access multiple-input multiple-output(MIMO) system 100 with access points and user terminals. For simplicity,only one access point 110 is shown in FIG. 1. An access point isgenerally a fixed station that communicates with the user terminals andmay also be referred to as a base station or some other terminology. Auser terminal may be fixed or mobile and may also be referred to as amobile station, a wireless device or some other terminology. Accesspoint 110 may communicate with one or more user terminals 120 at anygiven moment on the downlink and uplink. The downlink (i.e., forwardlink) is the communication link from the access point to the userterminals, and the uplink (i.e., reverse link) is the communication linkfrom the user terminals to the access point. A user terminal may alsocommunicate peer-to-peer with another user terminal. A system controller130 couples to and provides coordination and control for the accesspoints.

While portions of the following disclosure will describe user terminals120 capable of communicating via Spatial Division Multiple Access(SDMA), for certain aspects, the user terminals 120 may also includesome user terminals that do not support SDMA. Thus, for such aspects, anaccess point (AP) 110 may be configured to communicate with both SDMAand non-SDMA user terminals. This approach may conveniently allow olderversions of user terminals (“legacy” stations) to remain deployed in anenterprise, extending their useful lifetime, while allowing newer SDMAuser terminals to be introduced as deemed appropriate.

The system 100 employs multiple transmit and multiple receive antennasfor data transmission on the downlink and uplink. The access point 110is equipped with N_(ap) antennas and represents the multiple-input (MI)for downlink transmissions and the multiple-output (MO) for uplinktransmissions. A set of K selected user terminals 120 collectivelyrepresents the multiple-output for downlink transmissions and themultiple-input for uplink transmissions. For pure SDMA, it is desired tohave N_(ap)≧K≧1 if the data symbol streams for the K user terminals arenot multiplexed in code, frequency or time by some means. K may begreater than N_(ap) if the data symbol streams can be multiplexed usingTDMA technique, different code channels with CDMA, disjoint sets ofsubbands with OFDM, and so on. Each selected user terminal transmitsuser-specific data to and/or receives user-specific data from the accesspoint. In general, each selected user terminal may be equipped with oneor multiple antennas (i.e., N_(ut)≧1). The K selected user terminals canhave the same or different number of antennas.

The system 100 may be a time division duplex (TDD) system or a frequencydivision duplex (FDD) system. For a TDD system, the downlink and uplinkshare the same frequency band. For an FDD system, the downlink anduplink use different frequency bands. MIMO system 100 may also utilize asingle carrier or multiple carriers for transmission. Each user terminalmay be equipped with a single antenna (e.g., in order to keep costsdown) or multiple antennas (e.g., where the additional cost can besupported). The system 100 may also be a TDMA system if the userterminals 120 share the same frequency channel by dividingtransmission/reception into different time slots, each time slot beingassigned to different user terminal 120.

FIG. 2 illustrates a block diagram of access point 110 and two userterminals 120 m and 120 x in MIMO system 100. The access point 110 isequipped with N_(t) antennas 224 a through 224 t. User terminal 120 m isequipped with N_(ut,m) antennas 252 ma through 252 mu, and user terminal120 x is equipped with N_(ut,x) antennas 252 xa through 252 xu. Theaccess point 110 is a transmitting entity for the downlink and areceiving entity for the uplink. Each user terminal 120 is atransmitting entity for the uplink and a receiving entity for thedownlink. As used herein, a “transmitting entity” is an independentlyoperated apparatus or device capable of transmitting data via a wirelesschannel, and a “receiving entity” is an independently operated apparatusor device capable of receiving data via a wireless channel. In thefollowing description, the subscript “dn” denotes the downlink, thesubscript “up” denotes the uplink, Nup user terminals are selected forsimultaneous transmission on the uplink, Ndn user terminals are selectedfor simultaneous transmission on the downlink, Nup may or may not beequal to Ndn, and Nup and Ndn may be static values or can change foreach scheduling interval. The beam-steering or some other spatialprocessing technique may be used at the access point and user terminal.

On the uplink, at each user terminal 120 selected for uplinktransmission, a TX data processor 288 receives traffic data from a datasource 286 and control data from a controller 280. TX data processor 288processes (e.g., encodes, interleaves, and modulates) the traffic datafor the user terminal based on the coding and modulation schemesassociated with the rate selected for the user terminal and provides adata symbol stream. A TX spatial processor 290 performs spatialprocessing on the data symbol stream and provides N_(ut,m) transmitsymbol streams for the N_(ut,m) antennas. Each transmitter unit (TMTR)254 receives and processes (e.g., converts to analog, amplifies,filters, and frequency upconverts) a respective transmit symbol streamto generate an uplink signal. N_(ut,m) transmitter units 254 provideN_(ut,m) uplink signals for transmission from N_(ut,m) antennas 252 tothe access point.

Nup user terminals may be scheduled for simultaneous transmission on theuplink. Each of these user terminals performs spatial processing on itsdata symbol stream and transmits its set of transmit symbol streams onthe uplink to the access point.

At access point 110, N_(ap) antennas 224 a through 224 ap receive theuplink signals from all Nup user terminals transmitting on the uplink.Each antenna 224 provides a received signal to a respective receiverunit (RCVR) 222. Each receiver unit 222 performs processingcomplementary to that performed by transmitter unit 254 and provides areceived symbol stream. An RX spatial processor 240 performs receiverspatial processing on the N_(ap) received symbol streams from N_(ap)receiver units 222 and provides Nup recovered uplink data symbolstreams. The receiver spatial processing is performed in accordance withthe channel correlation matrix inversion (CCMI), minimum mean squareerror (MMSE), soft interference cancellation (SIC), or some othertechnique. Each recovered uplink data symbol stream is an estimate of adata symbol stream transmitted by a respective user terminal. An RX dataprocessor 242 processes (e.g., demodulates, deinterleaves, and decodes)each recovered uplink data symbol stream in accordance with the rateused for that stream to obtain decoded data. The decoded data for eachuser terminal may be provided to a data sink 244 for storage and/or acontroller 230 for further processing.

On the downlink, at access point 110, a TX data processor 210 receivestraffic data from a data source 208 for Ndn user terminals scheduled fordownlink transmission, control data from a controller 230, and possiblyother data from a scheduler 234. The various types of data may be senton different transport channels. TX data processor 210 processes (e.g.,encodes, interleaves, and modulates) the traffic data for each userterminal based on the rate selected for that user terminal. TX dataprocessor 210 provides Ndn downlink data symbol streams for the Ndn userterminals. A TX spatial processor 220 performs spatial processing (suchas a precoding or beamforming, as described in the present disclosure)on the Ndn downlink data symbol streams, and provides N_(ap) transmitsymbol streams for the N_(ap) antennas. Each transmitter unit 222receives and processes a respective transmit symbol stream to generate adownlink signal. N_(ap) transmitter units 222 providing N_(ap) downlinksignals for transmission from N_(ap) antennas 224 to the user terminals.

At each user terminal 120, N_(ut,m) antennas 252 receive the N_(ap)downlink signals from access point 110. Each receiver unit 254 processesa received signal from an associated antenna 252 and provides a receivedsymbol stream. An RX spatial processor 260 performs receiver spatialprocessing on N_(ut,m) received symbol streams from N_(ut,m) receiverunits 254 and provides a recovered downlink data symbol stream for theuser terminal. The receiver spatial processing is performed inaccordance with the CCMI, MMSE or some other technique. An RX dataprocessor 270 processes (e.g., demodulates, deinterleaves and decodes)the recovered downlink data symbol stream to obtain decoded data for theuser terminal.

At each user terminal 120, a channel estimator 278 estimates thedownlink channel response and provides downlink channel estimates, whichmay include channel gain estimates, SNR estimates, noise variance and soon. Similarly, a channel estimator 228 estimates the uplink channelresponse and provides uplink channel estimates. Controller 280 for eachuser terminal typically derives the spatial filter matrix for the userterminal based on the downlink channel response matrix H_(dn,m) for thatuser terminal. Controller 230 derives the spatial filter matrix for theaccess point based on the effective uplink channel response matrixH_(up,eff). Controller 280 for each user terminal may send feedbackinformation (e.g., the downlink and/or uplink eigenvectors, eigenvalues,SNR estimates, and so on) to the access point. Controllers 230 and 280also control the operation of various processing units at access point110 and user terminal 120, respectively.

As illustrated, in FIGS. 1 and 2, one or more user terminals 120 maysend one or more High Efficiency WLAN (HEW) packets 150, with a preambleformat as described herein (e.g., in accordance with one of the exampleformats shown in FIGS. 3A-4), to the access point 110 as part of a ULMU-MIMO transmission, for example. Each HEW packet 150 may betransmitted on a set of one or more spatial streams (e.g., up to 4). Forcertain aspects, the preamble portion of the HEW packet 150 may includetone-interleaved LTFs, subband-based LTFs, or hybrid LTFs (e.g., inaccordance with one of the example implementations illustrated in FIGS.10-13, 15, and 16).

The HEW packet 150 may be generated by a packet generating unit 287 atthe user terminal 120. The packet generating unit 287 may be implementedin the processing system of the user terminal 120, such as in the TXdata processor 288, the controller 280, and/or the data source 286.

After UL transmission, the HEW packet 150 may be processed (e.g.,decoded and interpreted) by a packet processing unit 243 at the accesspoint 110. The packet processing unit 243 may be implemented in theprocess system of the access point 110, such as in the RX spatialprocessor 240, the RX data processor 242, or the controller 230. Thepacket processing unit 243 may process received packets differently,based on the packet type (e.g., with which amendment to the IEEE 802.11standard the received packet complies). For example, the packetprocessing unit 243 may process a HEW packet 150 based on the IEEE802.11 HEW standard, but may interpret a legacy packet (e.g., a packetcomplying with IEEE 802.11a/b/g) in a different manner, according to thestandards amendment associated therewith.

Example Frame Format for Low Latency Channel Bonding

Aspects of the present disclosure provide techniques for reducinglatency in systems devices by transmitting legacy-decodable preambleinformation in each of multiple channels and for transmitting preambleinformation for channel estimation of a multi-channel transmission ingaps between the multiple channels.

The techniques may be used, for example, when transmitting in multiplechannels (e.g., double/triple/quadraple 802.11 bands), in systems withlegacy devices (capable of only communicating in a single band) need tobe informed about the multi-channel transmitted packet, so they canupdate their respective NAV even if they are working in single band.

One approach (e.g., for 802.11n and 802.11ac and 802.11ax STAs), is tosend preamble information (e.g., the preambles/CES/data that are sentprior to the multi-channel data), in all single channels overlapping themulti-channel. Since several estimations are required to enable doublechannel operation, the STAs are sending additional preamble\CES\Headerusing double channel (known as HT-STF and VHT-STF and HT-LTF and VHT-LTFin 802.11n and 802.11ac respectively).

An example of such a format is shown in FIG. 3. While this format allowsstations to achieve double channel estimations (via the HT/VHT fields)and single channel protection (via the legacy portion), it alsosignificantly increases latency.

Aspects of the present disclosure, however, provide techniques fordoubling the channel on wireless transmissions (e.g., for advanced orfuture generations of standard, such as 802.11 ad, or other standards),by sending additional preambles and channel estimation for themulti-channel in gaps between channels. This approach may still enablethe legacy single band receiver to be able to receive without anysignificant degradation (since header sensitivity may be very low, ˜−5dB) while allowing multiple channel stations to use (substantially) thesame time interval for all multi-channel estimations. Thus, thetechniques presented herein may help avoid at least some of theadditional latency described above with reference to FIG. 3.

FIG. 4 is a flow diagram of example operations 400 for generatingframes, in accordance with certain aspects of the present disclosure.The operations 400 may be performed by an apparatus, such as an AP(e.g., access point 110).

The operations 400 may begin, at 402, by generating a frame fortransmission on a plurality of channels, the frame having firstinformation comprising at least one of preamble, channel estimation, orheader information decodable and for processing by first and secondtypes of devices, and wherein the first information is repeated in eachof the plurality of channels during transmission of the frame, secondinformation comprising at least one of preamble, channel estimation, orheader information decodable and for processing by the second type ofdevice, and wherein the second information occupies gaps between thechannels during transmission of the frame, and a portion spanning theplurality of channels and the gaps. At 404, the frame is output fortransmission.

FIG. 5 is a flow diagram of example operations 500 for processing one ormore packets, in accordance with certain aspects of the presentdisclosure. The operations 500 may be performed by an apparatus, such asan STA (e.g., user terminal 120), and may be considered complementary tooperations 400 of FIG. 4.

The operations 500 begin, at 502, by obtaining a frame having firstinformation comprising at least one of preamble, channel estimation, orheader information decodable and for processing by first and secondtypes of wireless devices, the first information is repeated in each ofthe plurality of channels, second information comprising at least one ofpreamble, channel estimation, or header information decodable and forprocessing by the second type of device, and wherein the secondinformation occupies gaps between the channels, and a portion spanningthe plurality of channels and the gaps. At 504, station processes thefirst information and generates a channel estimate based, at least inpart, on the second information. At 506, the station decodes at leastsome of the remaining portion of the frame based on the channelestimate.

FIGS. 6, 7, 10-12, and 15-18 each show various frame preamble formats,in accordance with aspects of the present disclosure. In the case ofdata frames, the preambles will be followed by a DATA/Payload field(such as that shown in FIG. 3) and, in some cases, optional AGC & TRNfields (e.g., as in 802.11ad). The preamble formats described herein,however, may also be used in non-data frames (e.g., used for simplesignaling).

FIG. 6 illustrates an example legacy frame format 600 that may includelegacy fields (recognizable by legacy type devices), such as a legacyshort training field (L-STF), a legacy channel estimation field (L-CEF),and a legacy header (L-Header) field. As illustrated, these legacyfields may be repeated across multiple channels. For example, as shownat 610 and 620, the legacy format may be repeated across double ortriple channels. As illustrated, in either case, additional header andpreamble information may be sent after the legacy preamble, in anenhanced directional multi-gigabit (EDMG) header, to allow for channelestimation of subsequent multi-channel data (not shown). The legacypreamble may be followed by a (non-legacy) short training field (STF)and/or a (non-legacy) channel estimation field (CEF).

As illustrated in FIG. 7, however, rather than include this additionalinformation after the legacy preambles, the additional information maybe included earlier, in gap-fillers (GFs), using gaps between themultiple channels. For example, as shown at 710 and 720, the additionalinformation may be included in a single gap between double channels orin two gaps between triple channels. In general, for a transmission on nchannels, additional information could be transmitted in n−1 gaps.

As illustrated, assuming 1.76 GHz channels, the additional informationmay be transmitted in a 0.44 GHz gap (e.g., approximately ¼ the size ofeach of the channels). As illustrated, the additional information in thegap-filler may include a short training field (STF-GF) and/or a channelestimation (CE-GF) field. As shown, the frame may also includesubsequent header information (HEADER-GF), decodable by the second typeof device, occupying the same channels as the first preambleinformation.

As illustrated, the remaining portion comprises at least one of a shorttraining field (STF) spanning the plurality of channels and a field withinformation for channel estimation (CE) spanning the plurality ofchannels. A receiving station may decode a data portion of the remainingportion of the frame, based, at least in part, on the STF and CE fieldsspanning the plurality of channels.

Example Frame Formats for MIMO and/or Channel Bonding

Certain aspects of the present disclosure provide techniques forgenerating and processing frame structures with certain preambleinformation decodable by only certain types of devices. So called“Green-Field” preambles may be used, for example, in scenarios where itis assumed that other types of devices (e.g., legacy devices) are notpresent and, thus, do not need to be accommodated. Such preambles may beused with MIMO transmissions involving two or more spatial streams, aswell as channel bonding involving two or more channels.

FIG. 8 is a flow diagram of example operations 800 for generatingframes, in accordance with certain aspects of the present disclosure.The operations 800 may be performed by an apparatus, such as an AP(e.g., access point 110).

The operations 800 may begin, at 802, by generating a frame fortransmission on at least one channel, the frame having: a preambleportion comprising first information comprising at least one trainingfield detectable by other apparatuses, the first information to betransmitted on a set of one or more sub-channels, each sub-channelcomprising a fractional portion of the full bandwidth of the at leastone channel, and second information comprising at least one of channelestimation or header information, the second information to betransmitted using the full bandwidth of the at least one channel; and adata portion to be transmitted using the full bandwidth of the at leastone channel. At 804, the frame is output for transmission.

FIG. 9 is a flow diagram of example operations 900 for processing one ormore packets, in accordance with certain aspects of the presentdisclosure. The operations 900 may be performed by an apparatus, such asan STA (e.g., user terminal 120), and may be considered complementary tooperations 800 of FIG. 8.

The operations 900 begin, at 902, by obtaining a frame having: apreamble portion comprising first information comprising at least onetraining field detectable by other apparatuses, the first information tobe transmitted on a set of one or more sub-channels, each sub-channelcomprising a fractional portion of the full bandwidth of the at leastone channel, and second information comprising at least one of channelestimation or header information, the second information to betransmitted using the full bandwidth of the at least one channel. At904, the station processes the first information and generate a channelestimate based, at least in part, on the second information. At 906, thestation decodes at least some of the remaining portion of the framebased on the channel estimate.

FIGS. 10-12 illustrate example frame formats with (Green-Field)preambles for use with MIMO and/or channel bonding, in accordance withcertain aspects of the present disclosure. The preambles may have atraining field (e.g., a short training field STF) transmitted in arelatively narrow band that allows for FDMA-based detection by otherdevices.

FIG. 10 shows an example frame structure with such a preamble. Asillustrated, for a first station, STFs based on a first Golay code(Golay 1) may be transmitted on relatively narrowband channels (e.g.,17.6 MHz) within the wider channel bandwidth. As illustrated, for asecond station the STFs may be based on a second Golay code (Golay 2)and the frame may be transmitted in a second channel.

The STF may, for example, be formed with a Golay code of length of 16rather than 128. Such a structure may allow for low-power detection atthe receiver (<33 factor during the STF phase) and may allow multiplestations to work within the same band, fully utilizing the spatialseparation during the acquisition phase. Use of multiple bands in thismanner may help overcome channel frequency selectiveness (e.g., withdeliberate selection of the location of narrowband channel sets withinthe wider transmission channel).

As illustrated, the narrowband STFs may be followed by channelestimation sequences (CES) and header information spanning the width ofthe transmission channel. As illustrated in FIG. 10, different STAs mayuse different CES to reduce interference. The header information mayinclude information used to demodulate the data, and the headerinformation may be demodulated by all stations in range.

As described above, STF may be transmitted in relatively narrowbandchannels. For example, STF may be transmitted over a 17.6 MHz channel,with 100 such channels available for a 1.76 GHz transmission channel.Each transmission may use a set of N1 of these channels. In some cases,one N1 set of channels may be allocated for non-associated stations,while other sets of channels may allocated to associated stations (bythe AP).

As illustrated in FIG. 11, for MIMO transmissions, the station may use asimilar frame format, but with different sets of channels for STF foreach spatial stream. Further, as illustrated, a STA in MIMO mode may usemore CES for MIMO. The different sets of STF channels for the differentstreams may be non-overlapping. In this case, there may be no need forcyclic shift delay (CSD). While 2 spatial streams are shown as anexample, it should be understood that the techniques may be applied toany number of streams.

As illustrated in FIG. 12, a similar frame structure may also be usedfor transmissions with channel bonding (using bandwidth of two or morechannels). In this example, STF may be transmitted on all channels,while different STF frequencies may be used for the different (bonded)channels. CES and the (extended) header information (Ex-Header) may betransmitted on the bonded channels. In this case, there may be no needfor CSD. While 2 channels are shown as an example of channel bonding, itshould be understood that the techniques may be applied to any number ofbonded channels (and may include contiguous and/or non-contiguouschannels).

In some cases, similar preamble structures may be used for transmissionsusing both MIMO and channel bonding. In this case, the preamble formatmay be similar to that shown in FIG. 11, but across wider bandwidth dueto the bonded channels. As described above, STF may be transmitted anall (bonded) channels, but with different STF frequencies per spatialstream.

Certain aspects of the present disclosure also provide techniques forgenerating and processing frame structures with backward-compatiblepreambles (e.g., preambles with certain information decodable by legacydevices). These preambles may be used, for example, in non Green-Fieldscenarios, where different types of devices may be present.

FIG. 13 is a flow diagram of example operations 1300 for generatingframes, in accordance with certain aspects of the present disclosure.The operations 1300 may be performed by an apparatus, such as an AP(e.g., access point 110).

The operations 1300 may begin, at 1302, by generating a frame fortransmission on at least one channel, the frame having: firstinformation comprising at least one of a training field, channelestimation, or header information for processing by first and secondtypes of devices, and extended header information intended forprocessing by only a second type of device that is a targeted recipientof the frame; and a data portion to be transmitted on the at least onechannel. At 1304, the frame is output for transmission.

FIG. 14 is a flow diagram of example operations 1400 for processing oneor more packets, in accordance with certain aspects of the presentdisclosure. The operations 1400 may be performed by an apparatus, suchas an STA (e.g., user terminal 120), and may be considered complementaryto operations 1300 of FIG. 13.

The operations 1400 begin, at 1402, by obtaining a frame transmitted onat least one channel, the frame having: first information (e.g.,comprising at least one of a training field, channel estimation, orheader information) for processing by first and second types of devices,and extended header information intended for processing by only a secondtype of device that is a targeted recipient of the frame; and a dataportion to be transmitted on the at least one channel. At 1404, thestation processes the first information and, at 1406, the stationdecodes at least some of the data portion of the frame based on theextended header information.

FIGS. 15-18 illustrate example frame formats with backward-compatiblepreamble structures, in accordance with certain aspects of the presentdisclosure.

For example, FIG. 15 illustrates an example preamble structure that maybe used for transmissions without MIMO or channel bonding. Asillustrated, the preamble structure may maintain some legacy (e.g., IEEE802.11ad) preamble features, for example, with L-STFs, L-CEFs, andL-Header information. This may allow for maximum collision protection(by legacy and non-legacy devices).

As shown, however, the preamble structure may also include extendedheader information, for example, an enhanced directional multi-gigabit(EDMG) header to allow for new modes. While the header information mayinclude information used to demodulate the data, and the headerinformation may be demodulated by all stations in range. The extendedheard may include additional information that is used only for thereceiving station.

As illustrated in FIG. 16, a similar structure may be utilized forframes transmitted with channel bonding. In this case, legacy preambles,with L-STF, L-CES, and Header may be transmitted per channel, withextended headers, followed by a wider channel STF and CEF (due to thechannel bonding). The STF and CEF that follow the EDMG Headers may benew (e.g., non-legacy) sequences.

As illustrated in FIG. 17, a similar structure may be utilized forframes transmitted with MIMO, but without channel bonding. In this case,legacy preambles, with L-STF, L-CEF, and L-Header may be used perstream, with extended headers (e.g., EDMG Headers), followed by a(non-legacy) STF and CEFs. As with the channel bonding example, the STFand CEF that follow (e.g., CEF and -CEF) the EDMG Headers may be newsequences.

As shown, in some cases, the preamble for one stream may be delayed(relative to the other stream) by a cyclic shift delay (CSD) to allowfor distinguishing the two streams (transmitted on the same channel). Totime align the fields of the different streams after the preamble, a CSDmay be applied after the extended header for the stream whose preamblewas not initially delayed. As illustrated, the overall overhead in theillustrated example may be relatively low (e.g., 5.3 us for 4×4 MIMO).

While the illustrated examples shows MIMO of 2×2 by presenting one side,it should be understood that the techniques may be applied in a similarmanner to other MIMO cases (e.g., 3×3, 4×4, as well as non-symmetriccases n×m, with 1<=n<=4 & 1<=m<=4 & n< >m). In such cases, there may bea different CSD for each spatial stream.

As shown in FIG. 18, similar preamble structures may be used fortransmissions using both MIMO and channel bonding. In this case, thepreamble format may be a combination of the formats shown in FIGS. 16and 17. Again, using legacy preambles, with L-STF, L-CEF, and L-Header,per stream and per channel, may allow for enhanced collision protection.Adding the extended (EDMG) header information, followed by a widerchannel, MIMO STF, CEF, and CSD, may still result in a relatively lowoverall overhead (e.g., of 18 ns).

In the illustrated example, the preamble may be repeated in each of thebonded channels similar to that shown in FIG. 11, but across widerbandwidth due to the bonded channels. Similarly, for MIMO, the preamblemay be transmitted for each spatial stream, with the CSD applied todistinguish the preambles of the different streams, and to time alignthe wideband portions, such as (non-legacy) STF and CEFs (e.g., CEF and-CEF).

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering. For example, operations 400 and 500 illustrated inFIGS. 4 and 5 correspond to means 400A and 500A illustrated in FIGS. 4Aand 5A. Similarly, operations 800, 900, 1300 and 1400 illustrated inFIGS. 8, 9, 13, and 14 correspond to means 800A, 900A, 1300A and 1400Aillustrated in FIGS. 8A, 9A, 13A, and 14A.

For example, means for transmitting (or means for outputting fortransmission) may comprise a transmitter (e.g., the transmitter unit222) and/or an antenna(s) 224 of the access point 110 or the transmitterunit 254 and/or antenna(s) 252 of the user terminal 120 illustrated inFIG. 2. Means for receiving (or means for obtaining) may comprise areceiver (e.g., the receiver unit 222) and/or an antenna(s) 224 of theaccess point 110 or the receiver unit 254 and/or antenna(s) 254 of theuser terminal 120 illustrated in FIG. 2. Means for processing, means forgenerating, means for decoding, or means for determining, may comprise aprocessing system, which may include one or more processors, such as theRX data processor 242, the TX data processor 210, the TX spatialprocessor 220, and/or the controller 230 of the access point 110 or theRX data processor 270, the TX data processor 288, the TX spatialprocessor 290, and/or the controller 280 of the user terminal 120illustrated in FIG. 2.

In some cases, rather than actually transmitting a frame a device mayhave an interface to output a frame for transmission (a means foroutputting). For example, a processor may output a frame, via a businterface, to a radio frequency (RF) front end for transmission.Similarly, rather than actually receiving a frame, a device may have aninterface to obtain a frame received from another device (a means forobtaining). For example, a processor may obtain (or receive) a frame,via a bus interface, from an RF front end for reception.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thepresent disclosure may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in any form of storage medium that is knownin the art. Some examples of storage media that may be used includerandom access memory (RAM), read only memory (ROM), flash memory, EPROMmemory, EEPROM memory, registers, a hard disk, a removable disk, aCD-ROM and so forth. A software module may comprise a singleinstruction, or many instructions, and may be distributed over severaldifferent code segments, among different programs, and across multiplestorage media. A storage medium may be coupled to a processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware, or any combination thereof. If implemented in hardware, anexample hardware configuration may comprise a processing system in awireless node. The processing system may be implemented with a busarchitecture. The bus may include any number of interconnecting busesand bridges depending on the specific application of the processingsystem and the overall design constraints. The bus may link togethervarious circuits including a processor, machine-readable media, and abus interface. The bus interface may be used to connect a networkadapter, among other things, to the processing system via the bus. Thenetwork adapter may be used to implement the signal processing functionsof the PHY layer. In the case of a user terminal 120 (see FIG. 1), auser interface (e.g., keypad, display, mouse, joystick, etc.) may alsobe connected to the bus. The bus may also link various other circuitssuch as timing sources, peripherals, voltage regulators, powermanagement circuits, and the like, which are well known in the art, andtherefore, will not be described any further.

The processor may be responsible for managing the bus and generalprocessing, including the execution of software stored on themachine-readable media. The processor may be implemented with one ormore general-purpose and/or special-purpose processors. Examples includemicroprocessors, microcontrollers, DSP processors, and other circuitrythat can execute software. Software shall be construed broadly to meaninstructions, data, or any combination thereof, whether referred to assoftware, firmware, middleware, microcode, hardware descriptionlanguage, or otherwise. Machine-readable media may include, by way ofexample, RAM (Random Access Memory), flash memory, ROM (Read OnlyMemory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product. The computer-program product may comprisepackaging materials.

In a hardware implementation, the machine-readable media may be part ofthe processing system separate from the processor. However, as thoseskilled in the art will readily appreciate, the machine-readable media,or any portion thereof, may be external to the processing system. By wayof example, the machine-readable media may include a transmission line,a carrier wave modulated by data, and/or a computer product separatefrom the wireless node, all which may be accessed by the processorthrough the bus interface. Alternatively, or in addition, themachine-readable media, or any portion thereof, may be integrated intothe processor, such as the case may be with cache and/or generalregister files.

The processing system may be configured as a general-purpose processingsystem with one or more microprocessors providing the processorfunctionality and external memory providing at least a portion of themachine-readable media, all linked together with other supportingcircuitry through an external bus architecture. Alternatively, theprocessing system may be implemented with an ASIC (Application SpecificIntegrated Circuit) with the processor, the bus interface, the userinterface in the case of an access terminal), supporting circuitry, andat least a portion of the machine-readable media integrated into asingle chip, or with one or more FPGAs (Field Programmable Gate Arrays),PLDs (Programmable Logic Devices), controllers, state machines, gatedlogic, discrete hardware components, or any other suitable circuitry, orany combination of circuits that can perform the various functionalitydescribed throughout this disclosure. Those skilled in the art willrecognize how best to implement the described functionality for theprocessing system depending on the particular application and theoverall design constraints imposed on the overall system.

The machine-readable media may comprise a number of software modules.The software modules include instructions that, when executed by theprocessor, cause the processing system to perform various functions. Thesoftware modules may include a transmission module and a receivingmodule. Each software module may reside in a single storage device or bedistributed across multiple storage devices. By way of example, asoftware module may be loaded into RAM from a hard drive when atriggering event occurs. During execution of the software module, theprocessor may load some of the instructions into cache to increaseaccess speed. One or more cache lines may then be loaded into a generalregister file for execution by the processor. When referring to thefunctionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer-readable medium.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can comprise RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared (IR),radio, and microwave, then the coaxial cable, fiber optic cable, twistedpair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer program product may includepackaging material.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. An apparatus for wireless communications,comprising: a processing system configured to generate a frame fortransmission on at least one channel, the frame having: a preambleportion comprising first information comprising at least one trainingfield detectable by other apparatuses, the first information to betransmitted on a set of one or more sub-channels, each sub-channelcomprising a fractional portion of a full bandwidth of the at least onechannel, and second information comprising at least one of channelestimation or header information, the second information to betransmitted using the full bandwidth of the at least one channel, and adata portion to be transmitted using the full bandwidth of the at leastone channel; and an interface for outputting the frame for transmission.2. The apparatus of claim 1, wherein: the at least one channel comprisesat least a first channel for transmitting at least first and secondspatial streams; and the at least one training field comprises at leasta first training field for the first spatial stream to be transmitted ona first set of one or more sub-channels of the first channel, and atleast a second training field for the second spatial stream to betransmitted on a second set of one or more sub-channels of the firstchannel, wherein the first and second sets of sub-channels arenon-overlapping.
 3. The apparatus of claim 2, wherein the secondinformation comprises: at least first channel estimation information forthe first spatial stream to be transmitted using the full bandwidth ofthe first channel; and at least second channel estimation informationfor the second spatial stream to be transmitted using the full bandwidthof the first channel.
 4. The apparatus of claim 1, wherein: the at leastone channel comprises a set of channels assigned to the apparatus; andthe set of channels comprise at least two contiguous channels.
 5. Theapparatus of claim 1, wherein: the at least one channel comprises a setof channels assigned to the apparatus; the set of channels comprises atleast first and second channels assigned to the apparatus; the at leastone training field comprises at least a first training field to betransmitted on a set of one or more sub-channels of the first channeland at least a second training field to be transmitted on a set of oneor more sub-channels of the second channel, and the second informationcomprises channel estimation information to be transmitted usingcombined bandwidth of the first and second channels.
 6. The apparatus ofclaim 1, wherein: the at least one channel comprises a set of channelsassigned to the apparatus; the set of channels comprises at least firstand second channels for transmitting first and second spatial streams;and the at least one training field comprises at least a first trainingfield for the first spatial stream to be transmitted on a first set ofone or more sub-channels of each of the first and second channels, andat least a second training field for the second spatial stream to betransmitted on a second set of one or more sub-channels of each of thefirst and second channels; and the second information comprises channelestimation information to be transmitted using combined bandwidth of thefirst and second channels.
 7. The apparatus of claim 6, wherein at leastone of: the first and second sets of one or more sub-channels arenon-overlapping; or sub-channels used for the first and second spatialstreams are non-overlapping.
 8. The apparatus of claim 6, wherein thesecond information comprises: at least first channel estimationinformation for the first spatial stream to be transmitted usingcombined bandwidth of the first and second channels; and at least secondchannel estimation information for the second spatial stream to betransmitted using combined bandwidth of the first and second channels.9. An apparatus for wireless communications, comprising: an interfacefor obtaining, via at least one channel, a frame having: a preambleportion comprising first information comprising at least one trainingfield detectable by other apparatuses, the first information received ona set of one or more sub-channels, each sub-channel comprising afractional portion of a full bandwidth of the at least one channel,second information comprising at least one of channel estimation orheader information, the second information received using the fullbandwidth of the at least one channel, and a data portion transmittedusing the full bandwidth of the at least one channel; and a processingsystem configured to generate a channel estimate based, at least inpart, on the second information, and to decode at least some of the dataportion of the frame based on the channel estimate.
 10. The apparatus ofclaim 9, wherein: the at least one channel comprises at least a firstchannel for transmitting at least first and second spatial streams; andthe at least one training field comprises at least a first trainingfield for the first spatial stream received on a first set of one ormore sub-channels of the first channel, and at least a second trainingfield for the second spatial stream received on a second set of one ormore sub-channels of the first channel, wherein the first and secondsets of sub-channels are non-overlapping.
 11. The apparatus of claim 10,wherein the second information comprises: at least first channelestimation information for the first spatial stream received using thefull bandwidth of the first channel; and at least second channelestimation information for the second spatial stream received using thefull bandwidth of the first channel.
 12. The apparatus of claim 9,wherein: the at least one channel comprises a set of channels assignedto the apparatus; the set of channels comprises at least first andsecond channels assigned to the apparatus; the at least one trainingfield comprises at least a first training field received on a set of oneor more sub-channels of the first channel and at least a second trainingfield received on a set of one or more sub-channels of the secondchannel, and the second information comprises channel estimationinformation received using combined bandwidth of the first and secondchannels.
 13. The apparatus of claim 12, wherein: the set of channelscomprises at least first and second channels for transmitting first andsecond spatial streams; and the at least one training field comprises atleast a first training field for the first spatial stream to received ona first set of one or more sub-channels of each of the first and secondchannels, and at least a second training field for the second spatialstream received on a second set of one or more sub-channels of each ofthe first and second channels; and the second information compriseschannel estimation information received using combined bandwidth of thefirst and second channels.
 14. The apparatus of claim 12, wherein thesecond information comprises: at least first channel estimationinformation for the first spatial stream received using combinedbandwidth of the first and second channels; and at least second channelestimation information for the second spatial stream received usingcombined bandwidth of the first and second channels.
 15. An apparatusfor wireless communications, comprising: a processing system configuredto generate a frame for transmission on at least one channel, the framehaving: first information comprising at least one of a training field,channel estimation, or header information for processing by first andsecond types of devices, and extended header information intended forprocessing by only a second type of device that is a targeted recipientof the frame, and a data portion; and an interface for outputting theframe for transmission via the at least one channel.
 16. The apparatusof claim 15, wherein: the frame further comprises, for each of first andsecond spatial streams, second information comprising at least one of atraining field or channel estimation information for processing by thetargeted recipient of the frame; and wherein the second information forthe first spatial stream is output for transmission with a delayrelative to transmission of an end of the first information for thefirst spatial stream in order to time align the second information forthe first spatial stream with the second information for the secondspatial stream.
 17. The apparatus of claim 15, wherein: the at least onechannel comprises a set of channels assigned to the apparatus; and thedata portion is to be transmitted on bandwidth spanning the set ofchannels.
 18. The apparatus of claim 15, wherein: the at least onechannel comprises a set of channels assigned to the apparatus; the setof channels comprises at least first and second contiguous channels; thefirst information is repeated in each of the first and second channels;and the frame further comprises second information comprising at leastone of a training field or channel estimation information for processingby the targeted recipient of the frame, wherein the second informationis to be output for transmission on bandwidth spanning the at leastfirst and second channels.
 19. The apparatus of claim 18, wherein: thefirst and second channels are for transmitting at least first and secondspatial streams; and the first information comprises first informationfor the first spatial stream repeated in each of the first and secondchannels and first information for the second spatial stream repeated ineach of the first and second channels, wherein the first information forthe second spatial stream is output for transmission with a delayrelative to transmission of the first information for the first spatialstream.
 20. The apparatus of claim 19, wherein: the second informationfor the first spatial stream is output for transmission with a delayrelative to transmission of an end of the first information for thefirst spatial stream in order to time align the second information forthe first spatial stream with the second information for the secondspatial stream.
 21. An apparatus for wireless communications,comprising: an interface for obtaining a frame transmitted on at leastone channel, the frame having: first information for processing by firstand second types of devices, and header information intended forprocessing by only a second type of device that is a targeted recipientof the frame, and a data portion; a processing system configured toprocess the first information and to decode at least some of the dataportion of the frame based on the extended header information.
 22. Theapparatus of claim 21, wherein: the at least one channel comprises atleast a single channel for transmitting at least first and secondspatial streams; and the first information comprises first informationfor the first spatial stream and first information for the secondspatial stream transmitted on the same single channel, wherein receptionof the first information for the second spatial stream by the apparatusis delayed relative to transmission of the first information for thefirst spatial stream.
 23. The apparatus of claim 21, wherein: the atleast one channel comprises a set of channels assigned to the apparatus;and the data portion is received on bandwidth spanning the set ofchannels.
 24. The apparatus of claim 21, wherein: the at least onechannel comprises a set of channels assigned to the apparatus; the setof channels comprises at least first and second contiguous channels; thefirst information is repeated in each of the first and second channels;and the frame further comprises second information comprising at leastone of a training field or channel estimation information for processingby the targeted recipient of the frame, wherein the second informationis received on bandwidth spanning the at least first and secondchannels.
 25. The apparatus of claim 24, wherein: the first and secondchannels are for obtaining at least first and second spatial streams;and the first information comprises first information for the firstspatial stream repeated in each of the first and second channels andfirst information for the second spatial stream repeated in each of thefirst and second channels, wherein reception of the first informationfor the second spatial stream by the apparatus is delayed relative totransmission of the first information for the first spatial stream.26-83. (canceled)